Cluster availability management

ABSTRACT

A first logical partition in a first processing complex of a server cluster is operated in an active mode and a second logical partition in the processing complex is operated in a standby mode. Upon detection of a failure in a second processing complex of the server cluster. the standby mode logical partition in the first processing complex is activated to an active mode. In one embodiment, partition resources are transferred from an active mode logical partition to the logical partition activated from standby mode. Other embodiments are described and claimed.

RELATED APPLICATIONS

This application is a continuation application of copending parentapplication Ser. No. 11/168,973, filed Jun. 28, 2005, entitled “CLUSTERAVAILABILITY MANAGEMENT”, assigned to the assignee of the presentapplication and incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to management of a cluster in the event ofa failure.

2. Description of Related Art

In certain computing environments, multiple host systems may communicatewith a control unit, such as an IBM Enterprise Storage Server (ESS)®,for data in a storage device managed by the ESS receiving the request,providing access to storage devices, such as interconnected hard diskdrives through one or more logical paths. (IBM and ESS are registeredtrademarks of IBM). The interconnected drives may be configured as aDirect Access Storage Device (DASD), Redundant Array of IndependentDisks (RAID), Just a Bunch of Disks (JBOD), etc. The control unit, alsoknown as a cluster, may include duplicate and redundant processingnodes, also known as processing complexes, to allow for failover to asurviving processing complex in case one fails. The processing complexesmay access shared resources such as input/output (I/O) adapters, storageadapters and storage devices.

In the event a processing complex fails due to a hardware or softwarefailure, the surviving processing complex detects the failure and takescontrol of all shared resources of the cluster. The processing dutieswhich were being performed by the processing complex which failed aretaken over by the surviving processing complex.

The resources of each processing complex may be divided into a number oflogical partitions (LPAR), in which a computer's processors, memory, andhardware resources are divided into multiple environments. Eachenvironment can be operated independently, with its own operating systemand applications. Logical partitioning of a processing complex addsflexibility in workload management on a single server, with the abilityto partition the single machine into many logical servers with their ownsets of system resources. The resources in each partition may becombined in various amounts and combinations. Also, the number oflogical hardware partitions that can be created depends on the hardwaresystem.

Dynamic Logical Partitioning (DLPAR) extends the capability of LPAR byproviding the ability to logically attach and detach the resources of aprocessing complex to and from the operating system of a logicalpartition without rebooting. This resource allocation can occur not onlywhen activating a logical partition, but also while the partitions arerunning. Processor, memory, I/O adapter and other partition resourcescan be released into a “free pool,” acquired from that free pool, ormoved directly from one partition to another within a processingcomplex, in various amounts or combinations. However, each partitiongenerally has at least one processor, memory, an I/O adapter associatedwith a boot device, and a network adapter.

The movement of an LPAR resource from one hardware partition to anotherwithin a processing complex may be managed by a supervisor module. Totransfer a partition resource, the supervisor module can send a networkrequest to the logical partition which “owns” the partition resource,asking that source logical partition to release the particular partitionresource and put it into a quiesced state. In this manner, the partitionresource is stopped, and placed under control of a hypervisor module.The supervisor module can send a command to the hypervisor, instructingit to reallocate the partition resource from the source logicalpartition to a target logical partition. In addition, the supervisormodule can send a network request to the target logical partition,instructing it to acquire the partition resource from the hypervisormodule and configure it for use by the target logical partition.

SUMMARY

A first logical partition in a first processing complex of a servercluster is operated in an active mode and a second logical partition inthe processing complex is operated in a standby mode. Upon detection ofa failure in a second processing complex of the server cluster, thestandby mode logical partition in the first processing complex isactivated to an active mode. In one embodiment, partition resources aretransferred from an active mode logical partition to the logicalpartition activated from standby mode. Input/output or other processingoperations may be performed by both logical partitions in the survivingprocessing complex to provide redundancy until the other processingcomplex is repaired and reactivated. Other embodiments are described andclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a computing environment in which embodiments may beimplemented.

FIG. 2 illustrates one example of operations to handle a processingcomplex failure.

FIG. 3 is a schematic diagram of one example of a logical partition in astandby mode and a logical partition in an active mode.

FIG. 4 is a schematic diagram of one example of a logical partitionactivated to an active mode from a standby mode and a logical partitionin an active mode with reduced partition resources.

DETAILED DESCRIPTION

FIG. 1 illustrates one example of a computing environment in whichaspects of the present description may be employed. One or more hosts 2communicate Input/Output (I/O) requests directed to a storage system 4to a control unit or cluster 6, where the cluster 6 manages access tothe storage system 4. In one embodiment, the cluster 6 is comprised oftwo processing nodes or complexes 8 a, 8 b, each including a processor10 a, 10 b and a memory 12 12 a. Each processor 10 a, 10 b can include anumber of central processing units available as processing resources tothe associated processing complex 8 a, 8 b.

Each processing complex 8 a, 8 b includes a supervisor module 14 a, 14b. The supervisor modules 14 a, 14 b comprise code that manage andcoordinate the operations of one or more logical partitions 16 a, 16 bexecuting in the processing complexes 8 a, 8 b. Each logical partition16 a, 16 b separately executes an operating system 18 a, 18 b and devicedrivers 20 a, 20 b. The logical partitions comprise a division of theprocessors 10 a, 10 b into logical independent processing systems eachhaving their own operating systems 18 a, 18 b and device drivers 20 a,20 b. Multiple logical partitions may execute in each processingcomplex, managed by the supervisor module for that complex.

Each device driver 20 a, 20 b provides an interface between theoperating system 18 a, 18 b, in the logical partition 16 a, 16 b inwhich the device driver 20 a, 20 b executes, and an external device,such as host adaptors 22 a, 22 b . . . 22 n and device adaptors 24 a, 24b . . . 24 n. The host adaptors 22 a, 22 b . . . 22 n enable theprocessing complexes 8 a, 8 b to communicate with the hosts 2 and thedevice adaptors 24 a, 24 b . . . 24 n enable the processing complexes 8a, 8 b to communicate with the storage system 4. Thus, the processingcomplexes 8 a, 8 b share devices, such as adaptors 22 a, 22 b . . . 22n, 24 a, 24 b . . . 24 n. The variable “n” is used to denote an integerinstance of an element, and may indicate different or the same integervalue when used with different elements. For instance, 22 n and 24 n mayindicate a same or different number of host adaptors 22 n and deviceadaptors 24 n.

The processing complexes 8 a, 8 b communicate with the host adaptors 22a, 22 b . . . 22 n over a fabric 30 a and the device adaptors 24 a, 24 b. . . 24 n over a fabric 30 b. The fabrics 30 a, 30 b may comprise oneor more interfaces providing communication paths between the processingcomplexes 8 a, 8 b and adaptors. A path comprises the hardware in thefabrics 30 a, 30 b that enables communication with shared adaptors overthe fabric. In one embodiment, the fabric may comprise a Fibre Channelarbitrated loop configuration, a serial loop architecture or a businterface, such as a Peripheral Component Interconnect (PCI) interface.Each processing complex 8 a, 8 b may be assigned a portion of theadaptors 22 a, 22 b . . . 22 n, 24 a, 24 b . . . 24 n and duringinitialization, the processing complexes 8 a, 8 b are responsible forinitializing portions of the fabrics 30 a, 30 b providing communicationpaths to the adaptors that are assigned to that processing complex. Forinstance, if processing complex 8 a is assigned adaptors 22 a, 22 b, 24a, 24 b, then processing complex 8 a would initialize and configure thatportion of the fabric 30 a, 30 b providing communication paths betweenprocessing complex 8 a and adaptors 22 a, 22 b, 24 a, 24 b. Likewise, ifprocessing complex 8 b is assigned adaptors 22 n and 24 n, thenprocessing complex 8 b would initialize and configure that portion ofthe fabric 30 a, 30 b and paths enabling communication betweenprocessing complex 8 b and adaptors 22 n and 24 n. Configuring thefabrics 30 a, 30 b comprises setting registers in fabric hardware, e.g.,the Fibre Channel loop hardware, serial loop architecture hardware orbus interface hardware, and performing other initialization anddiscovery related operations. Each individual adaptor 22 a, 22 b . . .22 n, 24 a, 24 b . . . 24 n may be shared by the processing complexes 8a, 8 b.

The supervisor modules 14 a, 14 b in connection with a hypervisor module26 a, 26 b, maintain device/logical partition (LPAR) assignmentsidentifying each assignment of the adaptors 22 a, 22 b . . . 22 n, 24 a,24 b . . . 24 n to a logical partition 16 a, 16 b in each processingcomplex 8 a, 8 b, such that communication between a specific adaptor 22a, 22 b . . . 22 n, 24 a, 24 b . . . 24 n and the processing complex 8a, 8 b is handled by the device driver 20 a, 20 b executing in thelogical partition 16 a, 16 b assigned to the specific adaptor 22 a, 22 b. . . 22 n, 24 a, 24 b . . . 24 n.

Each processing complex 8 a, 8 b may be on separate power boundaries.The processing complexes 8 a, 8 b may be assigned to handle I/O requestsdirected to specific volumes configured in the storage system 4. Theprocessing complexes 8 a, 8 b communicate with the storage system 4, viathe device adaptors 24 a, 24 b . . . 24 n, over a device network (notshown), which may comprise a local area network (LAN), storage areanetwork (SAN), bus interface, serial interface, etc. Further, theprocessing complexes 8 a, 8 b communicate over a connection 28 enablingprocessor inter-communication to manage configuring operations performedwith respect to the shared devices, such as the shared adaptors 22 a, 22b . . . 22 n, 24 a, 24 b . . . 24 n. In alternative embodiments, theremay be only one fabric connecting all adaptors 22 a, 22 b . . . 24 n, 24a, 24 b . . . 24 n, i.e., fabrics 30 a and 30 b may be part of a singleinterconnected fabric, or two fabrics 30 a, 30 b as shown, or more thantwo fabrics.

The cluster 6 may comprise any type of server, such as an enterprisestorage server, storage controller, etc., or other device used to manageI/O requests to attached storage system(s) 4, where the storage systemsmay comprise one or more storage devices known in the art, such asinterconnected hard disk drives (e.g., configured as a DASD, RAID, JBOD,etc.), magnetic tape, electronic memory, etc. The hosts 2 maycommunicate with the cluster 6, via the adaptors 22 a, 22 b . . . 22 n,over a network (not shown), such as a Local Area Network (LAN), StorageArea Network (SAN), Wide Area Network (WAN), wireless network, etc.Alternatively, the hosts 2 may communicate with the cluster 6 over a businterface, such as a Peripheral Component Interconnect (PCI) bus orserial interface. It is further appreciated that the cluster 6 may alsobe, for example, a generic server cluster, not just a storage subsystemor storage controller. For example, the two servers could be IBM pSeriesservers running a highly available clustered application, such as LotusNotes®.

In accordance with one aspect of the present description, FIG. 2illustrates one example of operations of a cluster which increasesredundancy in the event of a hardware or software failure. In oneoperation, the cluster operates (block 200) in a first node orprocessing complex of the cluster, a first logical partition in anactive mode and a second logical partition in a standby mode. FIG. 3 isa diagram which schematically illustrates an example of the cluster 6operating a first logical partition 16 a 1 of the processing complex 8a, in an active mode. In addition, a second logical partition 16 a 2 ofthe processing complex 8 a is operated in a standby mode. Similarly, afirst logical partition 16 b 1 of the processing complex 8 b, may beoperated in an active mode, and a second logical partition 16 b 2 of theprocessing complex 8 b may be operated in a standby mode.

In the illustrated embodiment, in an active mode, the logical partitions16 a 1, 16 b 1, perform input/output operations on behalf of a host 2.For example, an active mode logical partition 16 a 1 may read data fromor write data to a storage system 4 as represented by the sharedresources 300 of FIG. 3. Each active logical partition 16 a 1, 16 b 1has access to additional shared resources 300 including the hostadapters 22 a, 22 b . . . 22 n to receive input/output tasks from a host2. These input/output tasks and their associated input/output data aretemporarily stored in memory assigned to the active mode logicalpartitions. Although the processing operations performed by the activelogical partitions are described as input/output operations on behalf ofa host 2, it is appreciated that the active logical partitions mayperform other types of processing operations.

The logical partitions 16 a 1, 16 b 1 each have access to additionalshared resources 300 including the device adaptors 24 a, 24 b . . . 24 nto write output data from a host 2 to the storage system 4 and toreceive from the storage system 4, read input data to forward to a host2 in accordance with the particular input/output operations beingperformed. To perform these input/output operations or other processingoperations, the active mode logical partitions are each assigned asubstantial portion of the partition resources of associated processingcomplex 8 a, 8 b. Thus, for example, the active mode logical partition16 a 1 may be assigned a majority of the CPU resources, memory resourcesand other dynamically assignable partition resources of the processingcomplex 8 a. The percentage of the dynamically assignable partitionresources assigned to any one active mode logical partition may dependupon the number of active mode and standby mode logical partitions in aprocessing complex and the relative workloads of each active modelogical partition.

By comparison, in the illustrated embodiment, in a standby mode, thelogical partitions 16 a 2, 16 b 2, do not perform input/outputoperations on behalf of a host 2 and do not have access to the sharedresources 300. Thus, for example, a standby mode logical partition 16 a2 does not read data from or write data to the storage system 4 ofshared resources 300 of FIG. 3. Each standby mode logical partition 16 a2, 16 b 2 does not have access to the shared host adapters 22 a, 22 b .. . 22 n since the standby mode logical partitions 16 a 2, 16 b 2 do notreceive input/output tasks from a host 2. Thus, input/output tasks andtheir associated input/output data are not stored in memory assigned tothe standby mode logical partitions.

Similarly, in the illustrated embodiment, the standby mode logicalpartitions 16 a 2, 16 b 2 do not have access to the device adaptors 24a, 24 b . . . 24 n of the shared resources 300 and do not write outputdata from a host 2 to the storage system 4. The standby mode logicalpartitions 16 a 2, 16 b 2 do not receive from the storage system 4, readinput data to forward to a host 2.

In that the standby mode logical partitions do not, in this example,perform input/output operations, the standby mode logical partitions 16a 2, 16 b 2 are each assigned a relatively small portion of thepartition resources of associated processing complex 8 a, 8 b. Thus, forexample, the active mode logical partition 16 a 1 may be assigned asingle CPU (or a fraction of a single CPU), and a small amount of thememory resources and other dynamically assignable partition resources ofthe processing complex 8 a as appropriate to maintain the standby mode.For example, a standby mode logical partition 16 a 2 may be assignedsufficient memory to maintain operation of an operating system butlittle or no additional operational memory may be needed.

In the illustrated embodiment, the active mode logical partition 16 a 1maintains state information in a data structure 302 a concerning thevarious states of the various state machines of the cluster 6. Asynchronized copy of the cluster state information is similarlymaintained by the active mode logical partition 16 b 1 in a datastructure 302 b. This state information facilitates control of theinput/output operations or other processing operations being performedby the active logical partitions 16 a 1, 16 b 1 of the cluster 6 onbehalf of a host 2. The active logical partitions 16 a 1, 16 b 1 mayexchange state information between each other to facilitate each activepartition maintaining current state information concerning clusteroperations. In addition, the active mode logical partitions maintaindata structures which facilitate performing the input/output operationsin response to input/output tasks received from the hosts 2. Theseadditional data structures maintained by an active mode logicalpartition include buffers, tables, memory regions, etc.

By comparison, the standby mode logical partitions 16 a 2, 16 b 2 do notperform I/O operations for a host 2 and do not maintain data structuresconcerning those I/O operations. The standby mode logical partitions 16a 2, 16 b 2 do not exchange cluster state information with other logicalpartitions.

It is appreciated that, in some embodiments, the standby mode logicalpartitions 16 a 2, 16 b 2 may perform limited I/O operations and mayhave limited access to shared resources 300. In some embodiments, thestandby mode logical partitions 16 a 2, 16 b 2 may maintain limitedcluster state data structures and limited I/O operation data structures.The quantities of these limited amounts may vary, depending upon theparticular application. However, in many embodiments, the operationsundertaken or data structures maintained by the standby mode logicalpartitions 16 a 2, 16 b 2 may be substantially less than that of theactive mode logical partitions.

In another operation, a failure in a second processing complex of thecluster is detected (block 202, FIG. 2). For example, the active modelogical partition 16 a 1 may detect that the processing complex 8 b hasfailed as represented by the strike-through symbol 400 in FIG. 4. In oneembodiment, the active mode logical partitions 16 a 1, 16 b 1 mayperiodically exchange messages, sometimes referred to as “heartbeats,”to inform the other processing complex that it is operational. Shouldthe active mode logical partition 16 a 1 fail to receive such aheartbeat message from the active mode logical partition 16 b 1, thelogical partition 16 a 1 may infer that the processing complex 8 b hassuffered a failure. In the event of a failure by the other processingcomplex 8 b, the surviving processor complex 8 a may perform a failoverin which the I/O operations not completed by the processor complex 8 bwould be taken over and completed by the surviving processor complex 8a. In addition, all new I/O operations from the host 2 would beperformed by the processor complex 8 a until the other processor complex8 b could be repaired and brought back on line.

With the processing complex 8 b nonoperational, the cluster 6 may lackthe redundancy which was provided by the processing complex 8 b. Hence,a hardware or software failure in the surviving processing complex 8 amay cause I/O operations in the cluster 6 to cease or may cause a lossof data.

In accordance with another aspect of the present description, the activemode logical partition 16 a 1 of the surviving processing complex 8 a,may activate (block 204) a second logical partition, such as the standbymode logical partition 16 a 2, for example, of the surviving processorcomplex 8 a, such that the logical partition 16 a 2 may be operated inactive mode as well. As explained in greater detail below, activating astandby mode logical partition to active mode may provide an increaseddegree of redundancy. Thus, should a software failure occur, forexample, in one of the active mode logical partitions 16 a 1, 16 a 2,operational software including data structures may be preserved in thesurviving active mode logical partition of the surviving processorcomplex 8 a.

In the illustrated embodiment, the active mode logical partition 16 a 1may be made aware of a logical partition operating in a standby mode,such as the logical partition 16 a 2, by the logical partitions 16 a 1,16 a 2 exchanging appropriate heartbeat messages. Upon detecting afailure of the other processing complex 8 b, the active mode logicalpartition 16 a 1 can cause the standby mode logical partition 16 a 2 toactivate itself to the active mode by sending a suitable message to thelogical partition 16 a 2.

To switch from standby mode to active mode, the logical partition 16 a 2may request from the active mode partition 16 a 1 a copy of the clusterstate information 302 a and begin to maintain its own synchronized copyof the cluster state information in a data structure 302 c (FIG. 4).Additional information which the standby mode logical partition 16 a 2may obtain from the active mode logical partition 16 a 1 includes listsof the hosts 2 which are not operational, and lists of the hosts 2 forwhich I/O operations are being performed by the cluster 6. The standbymode logical partition 16 a 2 may also obtain from the active modelogical partition 16 a 1 information for configuring the sharedresources 300 including the host adaptors 22 a, 22 b . . . 22 n and thedevice adaptors 24 a, 24 b . . . 24 n.

Once the logical partition 16 a 2 has received synchronized copies ofthe appropriate information, the logical partition 16 a 2 can configurethe shared resources 300 to permit use of the shared resources 300 bythe logical partition 16 a 2. In addition, the logical partition 16 a 2can maintain synchronized copies of the I/O operations data structuresused in performing the I/O operations by the cluster 6. Once the logicalpartition 16 a 2 is ready to receive I/O operations from the hosts 2, itcan become an active member of the cluster 6.

To facilitate operation of the logical partition 16 a 2 in an activemode, the partition resources of the other logical partition of theprocessing complex 8 a, such as the logical partition 16 a 1, may bereduced (block 206) to make additional partition resources available forthe logical partition 16 a 2 as it operates in the active mode. In theillustrated embodiment, dynamic redistribution of partition resourcesmay be accomplished by the modules 14 a, 26 a as part of a failover tothe active mode logical partition 16 a 1.

Thus, in this example, the active mode logical partition 16 a 1 upondetecting the failure of the other processing complex 8 b, may transmita message to the supervisor module 14 a as part of the failoveroperation by which the active mode logical partition takes over the I/Ooperations which were previously performed by the processing complex 8b. In response, the supervisor module 14 a can send a network request tothe active mode logical partition 16 a 1 which “owns” a particularpartition resource, asking the active mode logical partition 16 a 1 torelease the particular partition resource and put it into a quiescedstate. In this manner, a partition resource may be stopped, and placedunder control of the hypervisor module 26 a.

In another operation, the partition resources assigned to the logicalpartition being activated may be expanded (block 208). In this example,the supervisor module 26 a can send a command to the hypervisor module26 a, instructing it to reallocate a quiesced partition resource fromthe active logical partition 16 a 1 to the logical partition 16 a 2which is being activated from standby mode to active mode. In addition,the supervisor module 14 a can send a network request to the logicalpartition 16 a 2, instructing it to acquire the quiesced partitionresource from the hypervisor module 26 a and configure it for use by thelogical partition 16 a 2 transitioning to the active mode.

These operations of reducing the partition resources assigned to alogical partition such as the logical partition 16 a 1, and expandingthe partition resources assigned to a logical partition transitioning toactive mode, such as the logical partition 16 a 2, may be performed foras many partition resources as appropriate to balance the I/O workloadbetween the logical partitions 16 a 1, 6 a 2, as appropriate. As thelogical partition 16 a 2 gains partition resources such as additionalprocessing and memory resources, for example, the amount of input/outputor other processing operational workload which may be assumed by thelogical partition 16 a 2 increases.

In one aspect of the present description, the logical partition 16 a 2activated from a standby mode to an active mode of operation provides adegree of redundancy in the event of a failure. For example, if thelogical partition 16 a 1 experiences a software failure, input/outputoperations by the cluster 6 may continue since the activated logicalpartition 16 a 2 has maintained synchronized copies of the data and datastructures needed for input/output operations, including cluster stateinformation, input/output operation data etc.

In another operation, the processing complex 8 b which, in this example,experienced the initial failure, may be repaired (block 210). Once oneor more logical partitions 16 b 1, 16 b 2 are returned to active modeand are capable of performing input/output operations for one or morehosts 2, one of the logical partitions 16 a 1, 16 a 2 of the processingcomplex 8 a may be returned to standby mode. It is appreciated that alogical partition may be returned to standby mode for other purposes andin other circumstances.

To return a logical partition to standby mode, partition resources ofthat logical partition may be reduced (block 212). In this example, thelogical partition 16 a 2 may be returned to standby mode. It isappreciated that in other applications, the logical partition 16 a 2 mayremain in active mode and another logical partition such as the logicalpartition 16 a 1 may assume the standby mode.

In this example, the active mode logical partition 16 a 1 upon receivingdata structure synchronization information and other communications fromthe processing complex 8 b, indicating that one or more logicalpartitions 16 b 1, 16 b 2 are in active mode and are capable ofconducting input/output operations for the hosts 2, a failback operationis performed, transferring input/output operations back to theprocessing complex 8 b. In connection with the failback operation, thelogical partition 16 a 1 may transmit a message to the supervisor module14 a. In response, the supervisor module 14 a can send a network requestto the active mode logical partition 16 a 2 which “owns” a particularpartition resource, instructing the active mode logical partition 16 a 2to release the particular partition resource and put it into a quiescedstate. In this manner, a partition resource may be stopped, and placedunder control of the hypervisor module 26 a.

In another operation, the partition resources assigned to the remaininglogical partition may be expanded (block 214). In this example, thesupervisor module 26 a can send a command to the hypervisor module 26 a,instructing it to reallocate a quiesced partition resource from thelogical partition 16 a 2 back to the logical partition 16 a 1 which willremain in the active mode. In addition, the supervisor module 14 a cansend a network request to the logical partition 16 a 1, instructing itto acquire the quiesced partition resource from the hypervisor module 26a and configure it for use by the logical partition 16 a 1.

These operations of reducing the partition resources assigned to alogical partition transitioning to standby mode, such as the logicalpartition 16 a 2, and expanding the partition resources assigned to thelogical partition remaining in the active mode, such as the logicalpartition 16 a 1, may be performed for as many partition resources asappropriate for these respective modes. As the logical partition 16 a 1gains partition resources such as processing and memory resources, forexample, the amount of input/output or other processing operationalworkload which may be assumed by the logical partition 16 a 1 increases.

In another operation, the logical partition 16 a 2 may be quiesced(block 216) to the standby mode such that the logical partition 16 a 2may be operated (block 218) in the standby mode and the logicalpartition 16 a 1 may be operated in the active mode. In this standbymode, the partition resources utilized by the logical partition 16 a 2in the standby mode may be reduced to a minimum as noted above.Moreover, the operations to be performed by the logical partition 16 a 2in a standby mode may be reduced or eliminated. One such minimumoperation may include periodically issuing a heartbeat message to theactive mode logical partitions such as the logical partition 16 a 1,informing the active mode logical partitions of the existence of thestandby mode partition 16 a 2. It is appreciated that the amount ofpartition resources and operations assigned a logical partition in astandby mode may vary, depending upon the particular application.

Additional Embodiment Details

The described operations may be implemented as a method, apparatus orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in a tangible medium, where such tangible mediummay comprise hardware logic (e.g., an integrated circuit chip,Programmable Gate Array (PGA), Application Specific Integrated Circuit(ASIC), etc.) or a computer readable medium, such as magnetic storagemedium (e.g., hard disk drives, floppy disks, tape, etc.), opticalstorage (CD-ROMs, optical disks, etc.), volatile and non-volatile memorydevices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware,programmable logic, etc.). Code in the computer readable medium isaccessed and executed by a processor. The tangible medium in which thecode or logic is encoded may also comprise transmission signalspropagating through space or a transmission media, such as an opticalfiber, copper wire, etc. The transmission signal in which the code orlogic is encoded may further comprise a wireless signal, satellitetransmission, radio waves, infrared signals, Bluetooth, etc. Thetransmission signal in which the code or logic is encoded is capable ofbeing transmitted by a transmitting station and received by a receivingstation, where the code or logic encoded in the transmission signal maybe decoded and stored in hardware or a computer readable medium at thereceiving and transmitting stations or devices. Additionally, the“article of manufacture” may comprise a combination of hardware andsoftware components in which the code is embodied, processed, andexecuted. Of course, those skilled in the art will recognize that manymodifications may be made to this configuration without departing fromthe scope of the present invention, and that the article of manufacturemay comprise any information bearing medium known in the art.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, “the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the present invention(s)” unless expressly specifiedotherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise.

The terms “a”, “an” and “the” mean “one or more”, unless expresslyspecified otherwise.

Devices that are in communication with each other need not be incontinuous communication with each other, unless expressly specifiedotherwise. In addition, devices that are in communication with eachother may communicate directly or indirectly through one or moreintermediaries.

A description of an embodiment with several components in communicationwith each other does not imply that all such components are required. Onthe contrary a variety of optional components are described toillustrate the wide variety of possible embodiments of the presentinvention.

Further, although process operations, method operations, algorithms orthe like may be described in a sequential order, such processes, methodsand algorithms may be configured to work in alternate orders. In otherwords, any sequence or order of operations that may be described doesnot necessarily indicate a requirement that the operations be performedin that order. The operations of processes described herein may beperformed in any order practical. Further, some operations may beperformed simultaneously.

When a single device or article is described herein, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described herein (whether ornot they cooperate), it will be readily apparent that a singledevice/article may be used in place of the more than one device orarticle.

The functionality and/or the features of a device may be alternativelyembodied by one or more other devices which are not explicitly describedas having such functionality/features. Thus, other embodiments of thepresent invention need not include the device itself.

In the described embodiments, the cluster 6 included two processingcomplexes 8 a, 8 b. In additional embodiments, there may be more thantwo systems accessing a shared device. In such embodiments, one or moreof the processing complexes may maintain a logical partition in astandby mode and ready to be activated to provide redundancy in theevent of a failure in another processing complex.

Certain embodiments may be directed to a method for deploying computinginstruction by a person or automated processing integratingcomputer-readable code into a computing system, wherein the code incombination with the computing system is enabled to perform theoperations of the described embodiments.

The illustrated operations of FIG. 2 shows certain events occurring in acertain order. In alternative embodiments, certain operations may beperformed in a different order, modified or removed. Moreover, steps maybe added to the above described logic and still conform to the describedembodiments. Further, operations described herein may occur sequentiallyor certain operations may be processed in parallel. Yet further,operations may be performed by a single processing unit or bydistributed processing units.

Certain operations have been described as occurring between logicalpartitions in a peer to peer manner. Other operations have beendescribed as being accomplished with supervisory hardware or software.It is appreciated that operations may be accomplished either in a peerto peer approach or in a supervised approach or in a combination ofapproaches.

Processing operations being performed have been described as includinginput/output operations, for example. It is appreciated that other typesof processing operations may be performed on behalf of a host or as aserver.

A server cluster has been described above having two processingcomplexes, each of which having in regular operation an active modelogical partition and a standby mode logical partition. It isappreciated that in other embodiments, a server cluster may have asingle processing complex or more than two processing complexes, andeach processing complex may have more than one active or standby modelogical partition.

The foregoing description of various embodiments has been presented forthe purposes of illustration and description. It is not intended to beexhaustive or to limit the description to the precise form disclosed.Many modifications and variations are possible in light of the aboveteaching.

What is claimed is:
 1. A method, comprising: operating a first logicalpartition having transferable partition resources in a first physicalprocessing complex of a server cluster in an active mode which includesoperating an operating system and actively performing input/outputoperations between a host and a storage system, and a second logicalpartition having transferable partition resources in the same firstphysical processing complex and in a quiesced standby mode whichincludes operating an operating system but is otherwise substantiallyinactive as compared to said active mode wherein the transferablepartition resources transferred to the second logical partition in thequiesced standby mode are reduced as compared to the transferrablepartition resources transferred to the first logical partition in theactive mode; detecting a failure in a second physical processing complexdifferent from the first physical processing complex of the servercluster; in response to said failure detection, activating the standbylogical partition in the first physical processing complex to operate inan active mode so that both the first and second logical partitions ofthe first physical processing complex operate in the active mode; andsubsequent to activating the second logical partition, transferringpartition resources from the first logical partition to the secondlogical partition while the first logical partition remains in theactive mode; wherein said active mode operating includes providingaccess to a shared resource of data storage disk drives for a logicalpartition operating in an active mode and wherein said quiesced standbymode operating includes denying access to said shared resource of datastorage disk drives for a logical partition operating in a quiescedstandby mode.
 2. The method of claim 1 further comprising: repairingsaid second processing complex; and in response to said repair,quiescing the second logical partition to operate in a quiesced standbymode.
 3. The method of claim 1, further comprising: reducing thepartition resources of the first logical partition; and subsequent toactivating the second logical partition, increasing the partitionresources of the second logical partition.
 4. The method of claim 2,further comprising: subsequent to the repair of the second processingcomplex, transferring partition resources from the second logicalpartition to the first logical partition.
 5. The method of claim 2,further comprising: reducing the partition resources of the secondlogical partition; and subsequent to the repair of the second processingcomplex, increasing the partition resources of the first logicalpartition.
 6. The method of claim 1 further comprising: repairing saidsecond processing complex; subsequent to the repair of the secondprocessing complex, transferring partition resources from the secondlogical partition to the first logical partition; and quiescing thesecond logical partition to operate back in the quiesced standby mode.7. The method of claim 1 wherein said partition resources includeprocessing, memory and input/output adapter resources.
 8. A system foruse with a host and a storage system, comprising: a server clusterhaving a first physical processing complex and a second physicalprocessing complex, said first processing complex having a first logicalpartition having an operating system and transferable partitionresources including shared resource data storage drives, and a secondlogical partition in the same first physical processing complex, havingan operating system and transferable partition resources, said servercluster having logic adapted to: operate said first logical partition inan active mode which includes operating an operating system and activelyperforming input/output operations between a host and a storage system,and said second logical partition in a quiesced standby mode whichincludes operating an operating system but is otherwise substantiallyinactive as compared to said active mode wherein the transferablepartition resources transferred to the second logical partition in thequiesced standby mode are reduced as compared to the transferablepartition resources transferred to the first logical partition in theactive mode; detect a failure in said second processing complexdifferent from the first physical processing complex; in response tosaid failure detection, activate said second logical partition from saidquiesced standby mode to operate in an active mode so that both thefirst and second logical partitions of the first processing complexoperate in the active mode; and subsequent to activating the secondlogical partition, transfer partition resources from the first logicalpartition to the second logical partition while the first logicalpartition remains in the active mode; wherein operating in the activemode includes providing access to shared resource data storage diskdrives for a logical partition operating in an active mode and whereinoperating in said quiesced standby mode includes denying access to saidshared resource data storage disk drives for a logical partitionoperating in a quiesced standby mode.
 9. The system of claim 8 whereinsaid server cluster logic is further adapted to, in response to repairof the second processing complex, quiesce the second logical partitionfrom the active mode to operate in a quiesced standby mode.
 10. Thesystem of claim 8, wherein said first logical partition has partitionresources, and said server cluster logic is further adapted to: reducethe partition resources of the first logical partition; and subsequentto activation of the second logical partition, increase the partitionresources of the second logical partition.
 11. The system of claim 9,wherein said second logical partition has partition resources andwherein said server cluster logic is further adapted to, subsequent tothe repair of the second processing complex, transfer partitionresources from the second logical partition to the first logicalpartition.
 12. The system of claim 8, wherein said second logicalpartition has partition resources and wherein said server cluster logicis further adapted to: reduce the partition resources of the secondlogical partition; and subsequent to repair of the second processingcomplex, increase the partition resources of the first logicalpartition.
 13. The system of claim 8 wherein said first logicalpartition has partition resources, and said server cluster logic isfurther adapted to: subsequent to repair of the second processingcomplex, transfer partition resources from the second logical partitionto the first logical partition; and quiesce the second logical partitionfrom the active mode to operate back in the quiesced standby mode. 14.The system of claim 8 wherein said partition resources includeprocessing, memory and input/output adapter resources.
 15. An article ofmanufacture, comprising: a computer readable storage medium havingcomputer readable program code enabled to be executed by a system toperform operations, wherein the system has a server cluster having afirst physical processing complex and a second physical processingcomplex, said first processing complex having a first logical partitionhaving transferable partition resources including shared resource datastorage drives and a second logical partition having transferablepartition resources, and wherein the system executed operationscomprise: operating said first logical partition in an active mode whichincludes operating an operating system and actively performinginput/output operations between a host and a storage system and saidsecond logical partition in a quiesced standby mode which includesoperating an operating system but is otherwise substantially inactive ascompared to said active mode wherein the transferable partitionresources transferred to the second logical partition in the quiescedstandby mode are reduced as compared to the transferable partitionresources transferred to the first logical partition in the active mode;detecting a failure in said second processing complex different from thefirst physical processing complex; in response to said failuredetection, activating said second logical partition from said quiescedstandby mode to operate in an active mode so that both the first andsecond logical partitions of the first processing complex operate in theactive mode; and subsequent to activating the second logical partition,transferring partition resources from the first logical partition to thesecond logical partition while the first logical partition remains inthe active mode; wherein said active mode operating includes providingaccess to a shared resource of data storage disk drives for a logicalpartition operating in an active mode and wherein said quiesced standbymode operating includes denying access to said shared resource of datastorage disk drives for a logical partition operating in a quiescedstandby mode.
 16. The article of claim 15 and wherein said systemexecuted operations further comprise: repairing said second processingcomplex; and in response to repair of the second processing complex,quiescing the second logical partition from the active mode to operatein a quiesced standby mode.
 17. The article of claim 15, wherein saidfirst logical partition has partition resources, and wherein said systemexecuted operations further comprise: reducing the partition resourcesof the first logical partition; and subsequent to activation of thesecond logical partition, increasing the partition resources of thesecond logical partition.
 18. The article of claim 16, wherein saidsecond logical partition has partition resources and wherein said systemexecuted operations further comprise, subsequent to the repair of thesecond processing complex, transferring partition resources from thesecond logical partition to the first logical partition.
 19. The articleof claim 16, wherein said second logical partition has partitionresources and wherein said system executed operations further comprise:reducing the partition resources of the second logical partition; andsubsequent to the repair of the second processing complex, increasingthe partition resources of the first logical partition.
 20. The articleof claim 15 wherein said first logical partition has partitionresources, and wherein said system executed operations further comprise:subsequent to repair of the second processing complex, transferringpartition resources from the second logical partition to the firstlogical partition; and quiescing the second logical partition from theactive mode to operate back in the quiesced standby mode.
 21. Thearticle of claim 15 wherein said partition resources include processing,memory and input/output adapter resources.
 22. A method for deployingcomputing instructions, comprising: integrating computer-readable codeinto a system, wherein the system has a server cluster having a firstphysical processing complex and a second physical processing complex,said first processing complex having a first logical partition and asecond logical partition, and wherein the code in combination with thesystem is enabled to cause the system to perform: operating said firstlogical partition having transferable partition resources in an activemode which includes operating an operating system and activelyperforming input/output operations between a host and a storage systemand said second logical partition having transferable partitionresources in a quiesced standby mode which includes operating anoperating system but is otherwise substantially inactive as compared tosaid active mode wherein the transferable partition resourcestransferred to the second logical partition in the quiesced standby modeare reduced as compared to the transferrable partition resourcestransferred to the first logical partition in the active mode; detectinga failure in said second processing complex different from the firstphysical processing complex; in response to said failure detection,activating said second logical partition from said quiesced standby modeto operate in an active mode so that both the first and second logicalpartitions of the first processing complex operate in the active mode;and subsequent to activating the second logical partition, transferringpartition resources from the first logical partition to the secondlogical partition while the first logical partition remains in theactive mode; wherein said active mode operating includes providingaccess to a shared resource of data storage disk drives for a logicalpartition operating in an active mode and wherein said quiesced standbymode operating includes denying access to said shared resource of datastorage disk drives for a logical partition operating in a quiescedstandby mode.
 23. The method of claim 22 and wherein the code incombination with the system is further enabled to cause the system toperform: repairing said second processing complex; and in response torepair of the second processing complex, quiescing the second logicalpartition from the active mode to operate in a quiesced standby mode.24. The method of claim 22, wherein said first logical partition haspartition resources, and wherein the code in combination with the systemis further enabled to cause the system to perform: reducing thepartition resources of the first logical partition; and subsequent toactivation of the second logical partition, increasing the partitionresources of the second logical partition.
 25. The method of claim 23,wherein said second logical partition has partition resources andwherein the code in combination with the system is further enabled tocause the system to perform, subsequent to the repair of the secondprocessing complex, transferring partition resources from the secondlogical partition to the first logical partition.
 26. The method ofclaim 23, wherein said second logical partition has partition resourcesand wherein the code in combination with the system is further enabledto cause the system to perform: reducing the partition resources of thesecond logical partition; and subsequent to the repair of the secondprocessing complex, increasing the partition resources of the firstlogical partition.
 27. The method of claim 22 wherein said first logicalpartition has partition resources, and wherein the code in combinationwith the system is further enabled to cause the system to perform:subsequent to repair of the second processing complex, transferringpartition resources from the second logical partition to the firstlogical partition; and quiescing the second logical partition from theactive mode to operate back in the quiesced standby mode.
 28. The methodof claim 22 wherein said partition resources include processing, memoryand input/output adapter resources.